The following background information is provided to assist the reader to understand the disclosure provided below and the environment in which embodiments of the disclosed catheter will typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document.
Percutaneous transluminal angioplasty (PTA) is a medical procedure that is used to reduce or eliminate blockages within the vascular system in order to relieve clinical symptoms associated with reduced blood flow to an organ or region of the body. PTA works by placing a non-elastomeric balloon within a blockage and inflating it with sufficient force to enlarge stenotic lesions. The balloon compresses the atherosclerotic plaque to effectively enlarge a previously constricted lumen. This procedure has become a primary therapy for treatment of occlusive vascular disease.
A typical angioplasty interventional procedure starts with a puncture into the vascular system, usually in a femoral artery. Once access is gained, a first guidewire is placed through the center of the needle into the artery and the needle is removed. A sheath with a dilator of a given size, commonly called an introducer, is then placed over the guidewire into the artery to expand the puncture site and to maintain continuous access. The dilator and guidewire are then removed leaving the hemostasis valve of the introducer to seal against blood flow but allow access to the artery. A second guidewire and diagnostic catheter are then placed through the introducer into the vasculature with the guidewire going prior to the diagnostic catheter. Once the diagnostic catheter is placed over the second guidewire, that guidewire is removed and an injection of contrast fluid is usually done to visualize the peripheral vascular system and identify target lesions for revascularization. A third guidewire may be then inserted through the diagnostic catheter into the vascular system and positioned so the tip of the guidewire is distal to the target lesion. This guidewire protects the artery from damage as the balloon catheter traverses the vascular system after the diagnostic catheter has been removed. A balloon catheter is then flushed and the catheter tip loaded onto the guidewire after which the balloon catheter is inserted through the vascular introducer. The balloon catheter travels over the guidewire sometimes through rather tortuous vasculature and is positioned at the target lesion so that marker bands, which delineate the treatment area of the balloon, are positioned proximal and distal to the stenosis. A variable stiffness to this catheter can greatly enhance the ability of the interventionalist to traverse the vascular system and place the interventional catheter, in this case a balloon catheter, at the appropriate point for the procedure. The balloon is then inflated to the desired diameter and remains expanded for approximately one minute, after which it is deflated and the balloon catheter is removed from the vascular system. If additional procedures are necessary, the remaining guidewire functions to facilitate placement of any additional interventional devices. An injection of contrast is finally made to verify that the stenosis has been sufficiently dilated. Upon completion of the intervention, the guidewire and introducer are removed from the vascular system and the puncture wound sealed. The devices of the present disclosure utilize one or more retractable core wires within the balloon catheter to vary the stiffness of the catheter as it travels through a patient's vasculature.